1. Field of the Invention
This invention concerns the sector of equipment for moulding objects by means of molten metal castings. It specifically concerns the production of metal objects by feeding molten metal under pressure from a holding furnace to a mould placed on a press plate located above the furnace.
2. Description of the Related Art
At present many metal objects, such as vehicle wheel rims, are produced by the forced injection of molten metal into a mould.
The usual procedure is to keep the molten metal in holding furnaces; above the holding furnace there is a hydraulic press, on the bottom plate of which is placed the mould communicating with the bottom of the holding furnace by means of a vertical pipe; when the furnace is put under pressure, for example using compressed air, the molten metal goes up the pipe to the mould and fills it. The pressure exerted in the furnace is maintained until the casting inside the mould begins to solidify.
The pressure is then decreased to allow the metal inside the pipe to flow back into the furnace. This method for producing metal objects by injection casting is preferred to other methods because of the better product quality obtained and the speed of execution, even though the parts thus obtained have to be subjected to further surface processing. It is therefore necessary to produce objects with higher thicknesses (machining allowance); the objects may have internal imperfections that cannot be detected by the naked eye.